Modulation system



April 15, 1941. L. PUNGS 2,238,286

MODULATION SYSTEM Filed March 4, 1939 Leo Fangs by Httmwe;

Patented Apr. 15, 1941 UNITED STATES PATENT OF'FlCE MODULATION SYSTEM Leo Pungs, Brunswick, Germany Application March 4, 1939, Serial No. 259,721

Germany March 5, 1938 8 Claims. (01. na-rzrsj Cit oscillations having wavelengths equal to fractions of a meter are concerned. This absorption principle is generally realized by feeding a conventional electron tube, such as a triode, with high frequency currents either over Lecher wires or through an absorption circuit and by controlling the grid of such tube by modulation voltages applied thereto. However, severe difliculties occur when this principle is used in connection withoscillations having wavelengths shorter than fourtenths of a meter, since the electron tube introduces additional capacities in the circuits cooperatively connected therewith, from which follows that it will be hardly possible to maintain the grid of such tube at a desired value. A further disadvantage exists on account of the fact that the grid circuit together with its associated conductors or leads is coupled to the high frequency currents over the grid-plate capacity of such electron tube. It will readily be understood that a variety of uncontrollable by-pass paths are set up for the ultra high frequency currents which, if not entirely nullifying an effective utilization, at least give rise to considerable obstructions with respect to an effective operation.

My invention consists in certain features of novelty described in the following description and pointed out in the appended claims, reference being had to the accompanying drawing, in which:

Fig. l diagrammatically shows one embodiment of my invention, while Figs. 2 and 3 are modifications over the embodiment shown in Fig. l.

It is the mainobject of this invention to eliminate the disadvantages explained in the foregoing statement. This is realized according to the invention by the provision of a rectifier system through which the control currents are impressed upon the high frequency or system.

A corresponding arrangement is shown in Fig. 1 in which a Lecher s .stem L or similar arrangement is coupled to a high frequency device S which may be a transmitter or the like. In the Lecher system there are provided push-pull acting rectifiers GI and G2 which may be assumed to be push-pull connected diodes. It is thus obvious that rectified currents only can flow through the branch between the points A and absorption B indicated in i the Fig. 1. The actual modulating means, the impedance of which depends upon the degree of modulation involved is interposed in the heretofore mentioned direct current branch. This means may be a conventional triode M as shown in Fig. 1, to the grid circuit of which the low frequency modulating voltages from the voltage source Um are applied. There is no necessity for accommodating or matching this triode to ultra short wave operation since the two points between which thistriode is connected do not involve high frequency potentials against one another.

The above described arrangement is advantageous in many respects. For example, the rectifiers being the sole circuit elements in the high frequency circuit may be diodes each having a very low inherent capacity. Moreover, such diodes are more easily accommodated to the ultra short wave operating conditions than is the case with triodes, since the entire grid circuit arrangement is omitted. A further feature involved is that rectified currents only flow through the absorption resistance which. as seen from a high frequency point of view, may be considered as a direct current, or more precisely, as a tone frequency circuit.

It is obvious that the ratio of the impedance of the modulating triode to the impedances of the diodes must be correctly chosen in order to ensure effective modulation.

The aforementioned triode may easily be replaced by any other kind of voltage or current dependent resistances, or in other words, by any system presenting a non-linear characteristic. It would thus be "possible to use simple dryrectifiers and to control the resistance thereof by means of superposed voltages such as shown in Fig. 3. The resistance of the dry rectifier means R is controlled by the modulator Um and the voltage developed across the resistance X. The dry rectifier means may consist of a plurality of dry rectifiers or plates of a type well known in the art. The modulating source may further be connected directly in series with the dry rectifier means R. or the modulator may comprise a source of voltage in series with a dry rectifier means, and this modulator may be connected in parallel with the dry rectifier means R to superpose modulating voltages thereon.

The rectification may likewise be effected by means of a duplicate diode which is shownin Fig. 2 as-substitution for the two diodes of Fig. 1. The use of this duplicate diode involves the advantage of a more compact structure.

Provided that the direct current branch is adequately balanced, this branch may be located in any desired position without exerting any infiuence upon the oscillatory conditions of the generator system.

My present invention is by no means limited to the above described arrangement but is readily applicable in connection with any system for generating high frequency energies.

What is claimed is:

1. A modulating system comprising, a source for generating high frequency oscillations, a high frequency circuit coupled thereto, a source of low frequency modulation oscillations, impedance means connected with said last mentioned source and being variable in response to the amplitude of modulation oscillations applied thereto, and rectifying means connected to said high frequency circuit and in series With said impedance means, the current through said rectifier means being controlled by said variable impedance in accordance with the modulation oscillations generated in said last mentioned source.

2. A modulating system comprising, a source for generating high frequency oscillations, a high frequency circuit coupled thereto, a source of loW frequency modulation oscillations, impedance means connected with said last mentioned source and being variable in response to the amplitude of modulation oscillations applied thereto, and rectifying means connected to said high frequency circuit and to said impedance means to rectify high frequency oscillations in said high frequency circuit and to apply rectified high frequency energy to said impedance means.

3. A modulating system comprising, a source for generating high frequency oscillations, a high frequency circuit coupled thereto, a source of low frequency modulation oscillations, an electron discharge device having a cathode, a grid and an anode, said cathode and said grid being connected to said last mentioned modulation oscillations generating source, and rectifying means connected to said high frequency circuit and to the anode of said electron discharge device, the current through said rectifying means being varied in accordance with the modulation oscillations produced by said last mentioned source.

4. The invention according to claim 2, charact-erized in that said impedance means is a resistance having .a non-linear characteristic.

5. A modulating system comprising, a source for generating high frequency oscillations, a high frequency circuit coupled thereto, dry rectifier means connected in said high frequency circuit, means to vary the resistance of said dry rectifier means by superposed modulation currents, and rectifier means connected to said high frequency circuit and in series With said dry rectifier means, the current through said rectifier means being controlled by the variable resistance of said dry rectifier means in accordance with the superposed modulation currents.

6. The invention according to claim 1, characterized in that the said rectifying means is a double diode,

'7. The invention according to claim 2, characterized in that said rectifying means are two diodes connected for full wave rectification of the high frequency oscillations between said-high frequency circuit and said impedance means to apply rectified high frequency energy to said impedance means.

8. The invention according to claim 1, characterized in that the said high frequency circuit is a Lecher system.

LEO 'PUNGS. 

